"Did the, ah, 'inmates' choose to be there or was it a proper prison?" If they'd made the decision to go for help on their own, that made all the difference, but Sebastian still can't quite grasp how Snape ended up there. Unless this Admiral was daft enough to try and put him in place as a warden?

Then again, there is some cosmic irony to image of the Professor having to teach a class on anger management and basketweaving.